1. Field of the Invention
The present invention generally relates to rotating electrical machines and, more particularly, to such machines which have rotor windings connected to a group of diodes, formed as a package and mounted on the rotor.
2. Description of the Prior Art
Rotating electrical machines, such as motors and generators, have long been known and highly sophisticated designs have been developed over the years. Many advances have been made for the purpose of reducing size and cost of such electrical machines, among which has been the provision of a rotating diode package which is physically mounted on the rotor of the electrical machine to simplify assembly and reduce overall length of the machine. This type of arrangement is particularly applicable to electrical machines in which the rotor carries windings to which the diode package is electrically connected. A two pole generator, with reference to which the invention will be explained in detail, is typical of such machines.
Conventionally, the connection of the diode package to the rotor is made by the provision of a connector socket on the rotor which is adapted to receive connections formed on the diode package. The form of such diode packages has become standardized to simplify assembly and repair procedures and this portion of the connection is quite reliable. However, the connection of the connector to the rotor windings is usually formed by crimping the connector to the wire forming the rotor winding. Forming a terminal of the windings by crimping is desirable since it is quickly and easily done with very simple plier-like tools and the process can be automated with minimal tooling.
The deformation of both the connector and the wire lead during crimping causes some strain hardening of the metal of both elements. The length of these leads is not mechanically supported and is subject to stress from centrifugal forces when the machine is in operation as well as forces from angular acceleration and deceleration and vibration of the electrical machine, including rotational vibration. Also, the joint is subject to thermal stresses due to dissipation of heat from both the windings and the diode package. Additionally, the insertion of the pins or bolts into the connector disturbs the connection of the connector to the winding lead and induces further strain hardening and metal fatigue. For this reason, this particular electrical connection has a very high failure rate. Moreover, since such a structure is not easily susceptible to measurement of the degree of strain hardening which exists at a particular time, the failure rate is not easily reduced by maintenance procedures which, due to the requirement of disassembly and reassembly during maintenance, contributes to the development of strain hardening and brittleness. For this reason, any possible measurement of strain hardening would not reflect the condition of the connection after reassembly.
In addition, the use of such a connector tends to increase the overall length of the rotor and the overall length of the electrical machine without an increase in the power thereof. For many applications, the ability to minimize the size and weight of an electrical machine having given electrical specifications is critical to the suitability of a particular electrical machine for some applications, such as in aircraft systems.